SEGMENT REPORTING - Net Real Estate and Secured Note Payable Balances (Details) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net Real Estate		$ 2,045,964	$ 1,831,546
Secured Notes Payable	[1]	280,590	447,028
American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Net Real Estate		2,045,964	1,831,546
Secured notes payable, net | American Assets Trust, L.P.
Segment Reporting Information [Line Items]
Unamortized fair value adjustment and debt issuance costs		400	1,800
Total Retail
Segment Reporting Information [Line Items]
Net Real Estate		622,873	629,261
Secured Notes Payable	[1]	36,082	36,424
Total Office
Segment Reporting Information [Line Items]
Net Real Estate		812,437	813,414
Secured Notes Payable	[1]	170,764	206,550
Total Multifamily
Segment Reporting Information [Line Items]
Net Real Estate		427,333	203,014
Secured Notes Payable	[1]	73,744	73,744
Total Mixed-Use
Segment Reporting Information [Line Items]
Net Real Estate		183,321	185,857
Secured Notes Payable	[1]	$ 0	$ 130,310

[1] Excludes unamortized fair market value adjustments and debt issuance costs of $0.4 million and $1.8 million as of June 30, 2017 and December 31, 2016, respectively.